1. Field of the Invention
The present invention relates to a sheet feeder cassette provided with side stopper plates for defining the widthwise position of sheets of a recording medium stacked therein.
2. Description of Related Art
An image forming apparatus such as a color printer may be provided with a sheet feeder cassette that is capable of storing a large number of sheets (for example, 500 sheets) therein. The sheet feeder cassette is configured, for example, to be fitted into a sheet feeder unit of the image forming apparatus for image formation and to be drawn from the image forming apparatus for loading of sheets.
Referring to FIGS. 8, 9, 10a and 10b, the structure of a conventional sheet feeder cassette 100 is described. In each of the drawings, the arrow X shows a traveling direction or a lengthwise direction of sheets P stacked in the sheet feeder cassette 100. The arrow Y shows a fit-in direction in which the sheet feed cassette 100 is fitted into the sheet feeder unit or a widthwise direction of sheets P stacked in the sheet feeder cassette 100. The arrow Z shows the vertical direction.
The sheet feeder cassette 100 comprises a rectangular bottom 101, and a front panel 102, a right wall 103, a left wall 104 and a rear wall 105 that are arranged substantially perpendicularly to the bottom 101.
The sheet feeder cassette 100 further comprises side stopper plates 106 and 107 on the bottom 101. The side stopper plates 106 and 107 define the widthwise position of sheets P stacked on the bottom 101. In order to cope with various sheet sizes, the side stopper plates 106 and 107 are configured to be capable of sliding in the widthwise direction of the sheets P typically by the action of a rack-and-pinion mechanism.
In loading sheets in the sheet feeder cassette 100, as shown by FIG. 10a, a user leans a side of a stack of sheets against the right wall 103 and puts the stack of sheets on the bottom 101. If necessary, thereafter, the user moves the side stopper plates 106 and 107 by hand to define the widthwise position of the sheets P. Next, the user pushes the sheet feeder cassette 100 in the fit-in direction to fit the cassette 100 into a sheet feeder unit 200. When the cassette 100 is pushed to the rear end in the sheet feeder unit 200, as shown by FIG. 10b, the side stopper plate 106 receives force in the fit-in direction because the stack of sheets P tries to keep moving in the fit-in direction due to inertia. This causes a problem that the side stopper plate 106 may be displaced and/or deformed by the force.
In order to solve the problem, Japanese Patent Laid-Open Publication No. 2000-34022 teaches that a support member is provided between the rear wall and the side stopper plate. Japanese Patent Laid-Open Publication No. 2002-211770 discloses that in conjunction with a slide of the side stopper plate to a position suited for the sheet size, a fall preventive member for preventing the side stopper plate from falling moves to a position suited for the sheet size.
The standards of sheet sizes vary according to country and region. For example, in Japan, the sheet sizes typically used are based on the JIS B standard, while in the U.S., the sheet sizes typically used are based on the ANSI A-E standard. According to Japanese Patent Laid-Open Publication No. 2000-34022 and Japanese Patent Laid-Open Publication No. 2002-211770, however, it is necessary to adapt the support member and the fall preventive member to the sheet size standard typically used in the destination country.